1. Field of the Invention
This invention relates to a level wound coil (hereinafter called LWC) and, particularly, to an LWC that is formed winding a metal pipe, such as a copper and copper alloy pipe, which is used as a heat transfer pipe of an air-conditioning heat exchanger, a water pipe etc. Furthermore, this invention relates to a method of manufacturing the LWC and a package for the LWC.
2. Description of the Related Art
A heat transfer pipe such as an inner grooved tube/pipe and a smooth (plain) tube/pipe is used for the air-conditioning heat exchanger, the water pipe etc. The heat transfer pipe is typically formed of a copper or copper alloy pipe (hereinafter simply called copper pipe). In the manufacturing process thereof, the pipe is coiled and then annealed into a given tempered material. Then, it is stored or transported in the form of LWC. In use, the LWC is uncoiled and cut into a pipe example, JP-A-2002-370869 discloses a copper pipe feeding apparatus, which will be explained below.
FIG. 17A is a perspective view showing a conventional copper pipe feeding apparatus (vertical uncoiler). FIG. 17B is a perspective view showing a conventional copper pipe feeding apparatus (horizontal uncoiler).
As shown in FIG. 17A, the copper pipe feeding apparatus 10A is operated such that a bobbin 21 with an LWC 20 coiled around there is vertically attached, and a copper pipe 22 is fed from the bobbin 21 while being guided by a guide 11 in a feeding direction. Then, it is cut into a pipe with a desired length by a cutter (not shown).
As shown in FIG. 17B, the copper pipe feeding apparatus 10B is operated such that the bobbin 21 with the LWC 20 coiled around there is horizontally disposed on a turntable 12, and the copper pipe 22 is fed from the bobbin 21 while being guided by a guide 13 in a feeding direction. Then, it is cut into a pipe with a desired length by a cutter (not shown).
FIG. 18 is a cross sectional view showing a detailed arrangement of LWC coiled around the bobbin in FIG. 17A or 17B. As shown, the LWC 20 is structured with the copper pipe coiled around the bobbin 21. The bobbin 21 comprises an inner cylinder 23 around which the copper pipe 22 is coiled in multiple layers, and a pair of disk-like side boards 24 attached to both sides of the inner cylinder 23.
However, the copper pipe feeding apparatuses 10A, 10B as shown in FIGS. 17A and 17B have a problem that the structure is complicated and the cost thereof increases.
In order to solve this problem, JP-A-2002-370869 discloses a copper pipe feeding method called “Eye to the sky” (hereinafter called ETTS).
FIG. 19 is a perspective view showing the method of feeding a copper pipe by the ETTS method. An LWC assembly 30 has plural LWC's 32 that are stacked through a cushioning material 33 such that its center axis is directed perpendicularly to the upper surface of a pallet 31. The pallet 31 is usually formed rectangular and comprises plural wooden square logs 31a and one or more wooden board 31b attached on the square logs 31a. The cushioning material 33 is formed of wood, paper or plastics and has a disk shape with a greater diameter than the LWC 32.
As shown, the LWC 32 has an outside diameter of about 1000 mm and an inside diameter of 500 to 600 mm. The total height of the LWC assembly 30 including the pallet 31 is about 1 to 2 m.
The method of feeding a copper pipe by the ETTS method will be explained below referring to FIG. 19.
The copper pipe 35 is fed upward from the inside of the top LWC 32 in the LWC assembly 30. Then, in order to cut the copper pipe 35 on a pass line set horizontally about 1 m over the floor, the feeding direction is changed by a guide 34 disposed above the LWC assembly 30. Then, the copper pipe 35 is cut into a desired length by a cutter. A circular arc as the guide 34 is formed from a metal or plastic tube and has an inner diameter larger than an outer diameter of the copper pipe 35. The height from the plane on which to place the pallet 31 to the guide 34 is about 2.5 to 3.5 m.
The ETTS method is advantageous in removing the purchase cost of the bobbin since the bobbin 21 as shown in FIG. 18 is not needed. Further, as shown in FIG. 19, since it is not needed to rotate the LWC, the uncoiler and turntable as shown in FIGS. 17A and 17B are not needed. Thus, the facility cost can be significantly reduced.
A method of coiling the LWC 32 will be explained below referring to FIG. 18.
As shown in FIG. 18, for example, the copper pipe 22 is wound on the inner cylinder 23 of the bobbin 21 from a copper pipe 22a at start position to the right direction in alignment winding. The alignment winding is a method that the copper pipe 22 is wound in a circuit around the inner cylinder 23 and then it is wound in the next circuit in close contact with the previous circuit not to have a gap therebetween.
After the copper pipe 22 is wound up to the right end to have a cylinder form as the first layer, the second layer is wound on the first layer in alignment winding along the center-axis direction of the LWC from the right end to the left end (in the reverse direction). At that time the copper pipe of the second layer is arrayed in close-packed alignment to that of the first layer. Further, the third layer coil is formed on the second layer coil in the same way. This is called traverse winding, where after the first-layer cylindrical coil is formed, the second-layer cylindrical coil is wound in the reverse direction along the center-axis direction of the LWC. Thereby, the LWC can be reduced in volume and, therefore, a space needed in storing and transporting can be reduced.
FIG. 20 is a schematic cross sectional view illustrating an uncoiling method in LWC. FIG. 20 indicates the uncoiling state when the LWC 20 is uncoiled by the ETTS method, where the LWC 20 is produced such that the copper pipe 22 is wound around the bobbin 21 by the coiling method as shown in FIG. 18, removing the bobbin 21, disposing the LWC 20 on the cushioning material 33 as shown in FIG. 19. At first, the copper pipe 22a at start position on the inner layer side is fed upward. After the feeding of the first-layer is completed, the feeding of the second layer begins from a copper pipe 22b at lower end. Subsequently, the third layer adjoined outside of the second layer is fed from the upper end to the lower end.
However, the uncoiling method in LWC as shown in FIG. 20 has the next problems. When the LWC 20 is set as the LWC 32 in FIG. 19, the copper pipe 22b at lower end of the second layer is sandwiched between the cushioning material 33 (or the pallet 31) and a copper pipe 22 lying directly thereon. Therefore, it may be difficult to feed the copper pipe 22b due to the friction. When the friction in feeding is increased, the copper pipe 22 may be subjected to a bend or kink, resulting in product failure. Further, copper pipes 22b at the lower end of even-numbered layers, i.e., the second and fourth layers etc. can have the same problem.
In this regard, JP-A-2002-370869 discloses an uncoiling method to facilitate the feeding of a copper pipe at lower end in the ETTS method.
FIGS. 21 and 22 (corresponding to FIGS. 3 and 7, respectively, of JP-A-2002-370869) are schematic cross sectional views illustrating the uncoiling method to facilitate the feeding of a copper pipe at lower end.
One-side section of LWC 40 as shown in FIG. 21 is structured such that a copper pipe 41a at start position is located on the top, where an odd-numbered layer has n pipes (circuits) and an even-numbered layer has (n−1) pipes (circuits). The n is a natural number of 2 or more, typically 10 or more, and the pipes are wound in alignment winding.
In LWC 40 as shown in FIG. 21, the copper pipe 41a at start position on the inner layer side is fed upward. After the feeding of the first-layer is completed, the feeding of the second layer begins from a copper pipe 41b at lower end. In this case, since a gap exists between the copper pipe 41b at lower end of the second layer and the cushioning material 33 or pallet 31, the copper pipe 41b is less likely to be subjected to the resistance of the friction. Thus, the copper pipe 41 can be fed stably.
In contrast, FIG. 21 shows one-side section of LWC 40 that a copper pipe 41a at start position is located at the bottom close to the cushioning material 33. The copper pipe 41a at start position on the inner layer side is fed upward from the lower end to the upper end. After the feeding of the first-layer is completed, the feeding of the second layer begins from a copper pipe 41 at the upper end. In this case, since a copper pipe 41 at lower end of the second layer is not sandwiched when the copper pipe 41 turns upward, the copper pipe 41 can be fed stably as well as the case in FIG. 21.
Meanwhile, the above is taught in paragraphs [0009] to [0012], [0014] to [0017], [0039], [0042], [0062], and [0063] and FIGS. 3, 7 and 14 of JP-A-2002-370869.
However, the uncoiling method of JP-A-2002-370869 has the next problem. In the LWC wound as shown in FIG. 21, a circuit from the copper pipe 41 at lower end of the first layer to the copper pipe 41b at lower end of the second layer is exactly formed of a continuous copper pipe, though seen as separate pipes in the cross sectional view of FIG. 21. Thus, the copper pipe 41 is continuously shifted upward in a shift section on the circuit. When the length of the shift section increases, the gap between the copper pipe 41b at lower end of the second layer and the cushioning material 33 or pallet 31 may substantially disappear. Namely, the copper pipe 41b at lower end of the second layer may be sandwiched between the cushioning material 33 or the pallet 31 and the copper pipe 41 lying directly thereon. Therefore, it may be difficult to feed the copper pipe 41 and the copper pipe 41 may be subjected to a bend or kink.
The shift section that the copper pipe is shifted to the next-layer (i.e., the outer layer) will be detailed below referring to FIGS. 23A and 23B.
FIG. 23A is a schematic cross sectional view illustrating a portion without the shift section in LWC, and FIG. 23B is a schematic cross sectional view illustrating a portion with the shift section in LWC. In FIGS. 23A and 23B, an arrow passing through each pipe means that the LWC is uncoiled along the arrow direction. In the portion without the shift section as shown in FIG. 23A, of neighboring two layers, the outer layer has n−1 or n+1 stacked pipes when the inner layer has n stacked pipes. However, in the portion with the shift section 3 as shown in FIG. 23B, the outer layer also has n stacked pipes. Furthermore, with respect to the arrangement (positional relationship) of the neighboring layers of the copper pipe 2, a stack column (herein, a stack column means a column of the stacked copper pipes in a vertical section when LWC is vertically cut along a radius of LWC) in the portion without the shift section is arranged being fitted into a concave part formed in at least one of the neighboring stack columns (on the inner and outer sides). In contrast, a stack column (e.g., the fourth layer in FIG. 23B) in the portion with the shift section is arranged contacting a convex part formed in the neighboring stack columns. When the copper pipe 2 is fed as shown in FIG. 23B, the fourth-layer copper pipe at lower end of the shift section 3 may be sandwiched between a copper pipe lying directly thereon and the cushioning material (or coil spacer) lying under the LWC. As a result, the copper pipe will be trapped by them.